1. Technical Field
The present invention relates to a physical quantity sensor, a sensor unit, an electronic apparatus, a moving object, and a physical quantity detection method.
2. Related Art
In a device in which an acceleration sensor element is provided, other sensor elements (for example, a gyro sensor element, a pulse sensor element, a dynamics sensor element) are often used together therewith without being limited to a case where the acceleration sensor element is mounted independently. In a method disclosed in JP-A-9-243366, an analog output signal from an acceleration sensor element and a gyro sensor element is A/D converted using a common digital analog (A/D) converter. According to the method disclosed in JP-A-9-243366, highly accurate synchronization becomes possible by generating the conversion timing of the A/D converter using a high-accuracy external clock or the like.
In the method disclosed in JP-A-9-243366, however, in order to acquire an analog output signal from the acceleration sensor and the gyro sensor, it is necessary to operate the acceleration sensor and the gyro sensor constantly. Therefore, it is difficult to reduce power consumption.
On the other hand, in the case of forming the acceleration sensor using an acceleration sensor element and an IC, the IC is operated by an internal oscillation circuit, and the acceleration sensor element is measured at a measurement timing according to the oscillation frequency of the internal oscillation circuit. When a plurality of types of sensors are mounted in a device, it is difficult to achieve a precise synchronization between the measurement timing of the acceleration sensor according to the internal oscillation circuit and the measurement timing in the other sensors. In addition, there is also a case where the oscillation clock of the internal oscillation circuit for the acceleration sensor element and the operating system clock of a CPU for processing the acceleration measurement value in a device connected to the acceleration sensor need to be synchronized with each other. In order to obtain accurate frequency components of the acceleration measurement value, it may be necessary to perform measurement in synchronization with the high-accuracy external clock without depending on the internal clock.
In particular, when performing measurement at a minimum sampling rate for reducing power consumption, there is a possibility that a large difference may occur between the read time and the actual measurement time due to simply reading the acceleration measurement value held in the register.